The purpose of this project is to define hemostatic regulatory mechanisms of the brain. Because thrombo-occlusive processes are so important for stroke pathophysiology, brain regulation of hemostasis is a critical issue. Our data suggest that astrocyte- endothelial interactions at the blood-brain barrier provide a unique hemostatic regulatory system for the brain; moreover, this brain- specific regulatory system appears to have effects that are largely procoagulant. We will further define these astrocyte-endothelial interactions by analysis of hemostatic function of bovine brain capillary endothelial cells grown in monolayers and capillary-like structures. We will determine the hemostatic effects of diffusible factors elaborate by astrocytes and brain capillary endothelial cells. We will define the role of trnsformaing growth factor-beta (TGF-beta) as a mediator of brain hemostasis expression by analyzing TGF-beta synthesis and activation in our cell culture systems. Finally, we will delineate the effects of hypoxic-ischemic injury on brain regulation of hemostasis by exposure of our cell culture systems to severe hypoxia, with and without substrate deprivation, for period of 6-24 hours. Our findings will define pathways of brain regulation of hemostasis and pave the way for pharmacotherapies designed to prevent and treat strike by enhancement of the brain~s endogenous anticoagulant system.